Process cheeses are blends of natural cheese, emulsifying salts and other ingredients. The blends are generally processed into a molten sol by heating and blending. During processing, the molten sol may destabilize causing the fat to separate. Emulsifying salts such as sodium phosphate help prevent fat separation and control the pH of cheese.
Fat separation is prevented, or the fat is re-incorporated in the homogenous mixture during the heating and cooking process using the emulsifying salts. The emulsifying salts participate in an ion exchange reaction with caseins, the main protein source in natural cheese. The ion exchange process involves the removal of calcium from the insoluble collodial calcium phosphate complexes that stabilize casein-casein interactions in the gel matrix of the cheese. In effect, the divalent cation calcium is replaced by the monovalent cation sodium within the casein matrix through this process, solubilizing the colloidal calcium phosphate complex, converting calcium caseinate to sodium caseinate. Once the calcium is separated from the casein, the more hydrophobic regions of the casein can more effectively interact with the milk fat and the more hydrophilic regions of the casein can more effectively interact with the water transitioning from a gel state to a sol state. Thus, when the casein is separated from calcium, it acts as an emulsifier to stabilize the sol, thus allowing the components to combine. Upon cooling the transition from the sol state to a gel state is complete wherein the hydrated protein matrix stabilizes the fat in the product.
Emulsifying salts also control the pH of the cheese, which facilitates the organoleptic properties of the cheese by keeping the cheese from being too acidic or basic.
These salts also contribute to providing a smooth, creamy texture of the finished product and enable slices and spreads with varying firmness and melting properties to be produced. For example, process cheese may be poured into molds or shaped into slices and may resist melting, while some process cheese spreads melt readily to provide a pourable product.
Although emulsifying salts are required for the production of process cheese, their addition results in process cheese products having a relatively high sodium concentration compared to their natural cheese counterparts.